Research in human genetics has permitted the localization of a number of genes that confer an increased risk of cancer. BRCA1 is a genetic locus that is associated with an increased risk of breast and ovarian cancer in some families. A large kindred residing in Utah and Idaho has been extensively studied at the University of Utah and found to have markers on chromosome 17q that are tightly linked with the BRCA1 gene. This kindred (K2082) is the largest 17q linked breast cancer family reported to date by any group. It is now possible to accurately test individuals in this kindred for the presence of this gene. For women, the presence of the gene substantially increases their lifetime risk of breast and ovarian cancer. Men who are gene carriers appear to have no associated health risks, but are at risk for transmitting the gene to their children. At the present time, knowledge of how individuals and families will respond to this type of information is limited. This research project will offer genetic testing to approximately 400 adult men and women in this kindred and provide them with individual results and counseling within a structured, multidisciplinary clinical environment. Women and men who are both gene positive and gene negative will be evaluated before testing and 1 week, 3 months, 1 year, and 2 years after testing to assess the psychosocial impact of the information on individuals and families. In addition, the use of preventive health services and individual health related behaviors will be evaluated pre and post genetic testing. The findings of this study will be important for our understanding of the psychological and behavioral responses to predictive testing for breast and ovarian cancer. Such an understanding is essential to the development of safe and effective genetic testing and counseling protocols for these forms of cancer. The results also may assist in the development of predictive genetic testing protocols for other serious, adult onset conditions.